The present invention relates to a system having a supervisory module and one or more supervised modules mounted on separate circuit cards in a single housing.
One example of this type of system is a communication switch having line interface modules connectable to various types of electrical and optical communication lines. A single supervisory module in the switch initializes the line interface modules, monitors their status during subsequent operation, runs diagnostic tests, and responds to alarms and other conditions by changing register settings in the integrated circuits in the line interface modules.
The supervisory module communicates with the line interface modules through supervisory interface circuits in the line interface modules. In conventional switching systems of this type, the supervisory interface circuits provide read and write access to the registers in the integrated circuits in a line interface module by having a processor in the line interface module specify the physical addresses of the registers.
The physical address of a register depends on the internal structure of the integrated circuit in which the register is disposed, and the way in which the integrated circuit is connected to the supervisory interface circuit. The physical addresses of all of the registers in the line interface modules must be programmed into the supervisory module. The supervisory module must also be programmed with all of the initial register settings that must be made in each integrated circuit in each line interface module.
A resulting problem is that when the internal configuration or initial settings of a line interface module are changed, the software of the supervisory module must also be changed. These software changes are time-consuming, and the altered software must be tested, which takes further time. System development and maintenance become troublesome and difficult, because each change in a line interface module requires a corresponding change in the supervisory module. The troubles and difficulties are multiplied if the change alters not only register addresses, but also the meaning of the information placed in the registers.
These problems are not limited to line interface modules in switching systems.